Recently, a Low-k film is used as an interlayer insulating film in order to decrease an inter-wiring capacitance in response to the demand for high-speed of semiconductor devices or the like. As for the Low-k film, a film having a lower k value is preferred. Thus, a porous Low-k film is used as the Low-k film, and this makes it difficult to perform etching during formation of a wiring of BEOL (Back End Of Line).
Therefore, when the Low-k is used as an etching target film, a hard TiN film having high etching resistance is used as a metal hard mask serving as an etching mask in order to improve precision of etching processing or reduce damages inflicted on the Low-k film during asking or etching.
Although a PVD (Physical Vapor Deposition) method is currently mainly used as a method for forming a TiN film used for a metal hard mask, there is also examined a CVD (Chemical Vapor Deposition) method using TiCl4 gas as a Ti-containing gas and a nitriding gas (e.g., Japanese Patent Application Publication No. H06-188205) which is often used as a conventional TiN film forming method. Further, a SFD (Sequential Flow Deposition) method for alternately repeating formation of a TiN film and nitriding using TiCl4 gas and a nitriding gas or an ALD (Atomic Layer Deposition) method for alternately supplying TiCl4 gas and a nitriding gas (see, e.g., Japanese Patent Application Publication No. 2003-077864), which is one of the CVD method, is also examined as a method for forming a TiN film used for a metal hard mask.
The TiN film used for the metal hard mask needs to have high density. Therefore, the film formation using a plasma CVD method capable of forming a denser film is examined.
However, it has been found that when the TiN film is formed by the plasma CVD method (including the SFD method or the ALD method), the number of particles is tended to be increased after the number of substrates subjected to the TiN film formation exceeds about 150. If the number of particles is increased, the cleaning should be performed. The increase of the frequency of the cleaning leads to the decrease of the throughput.